This invention relates to apparatus for stabilizing, shoring, and raising foundations for buildings.
In certain soil conditions, a common problem encountered is the settling of the foundations of buildings, with resultant damage to building structures, including cracks and fissures. This problem has been addressed rather extensively in the prior art through the development and use of various types of foundation shoring and lifting devices incorporating a bracket which engages the footing or vertical wall of a building foundation in such a way that the upward, reaction force of a hydraulic cylinder utilized in combination with the foundation bracket to drive pilings or pier-pipe into the ground under the foundation is transmitted to and resisted by the weight of the building. U.S. Pat. No's. 4,678,373 and 3,902,326 to Langenbach, U.S. Pat. No. 2,982,103 to Revesz et al, U.S. Pat. No. 3,852,970 to Cassidy, and U.S. Pat. No. 4,708,528 to Rippe all disclose such types of apparatus incorporating a hydraulic cylinder supported above and directly in line with piling sections to be successively driven into the ground and coupled together so as to form a continuous, vertically extending pipe-pier or piling for supporting a foundation by connection to the aforesaid foundation bracket. Langenbach and Rippe, as well as Shaw et al in U.S. Pat. No. 4,673,315, disclose that the pilings should be driven downwardly until bedrock or load-bearing strata is reached, after which continued driving force applied downwardly to the piling by the hydraulic drive cylinder causes an upward reaction force which may be utilized to lift a foundation back upwardly to the desired elevation.
With the exception of Shaw et al, all of the aforesaid prior art devices mount the hydraulic drive cylinder at a particularly high location along the side wall of a building by means of a vertically extending support structure that is secured to the foundation bracket, with the downwardly extending piston of the hydraulic cylinder impacting on the top end of the pilings or pier-pipes which are successively driven into the ground. Such arrangements present a problem as to being able to drive the full length of each piling section into the ground, because the stroke of the piston is not long enough to drive a piling of the desired length completely from an above-ground location down into the ground. Revesz addresses this problem by the use of a cross-brace from which his hydraulic drive cylinder is suspended downwardly, with the brace being adjustable vertically along a pair of upwardly extending support posts which are secured at their lower ends to the foundation bracket. Rippe utilizes a separate spacer bar mounted between the bottom of the downwardly extending cylinder piston and the top of a pier section in order to permit his cylinder to fully drive a pier section into the ground over its entire length.
As disclosed in U.S. Pat. No. 4,673,315, Shaw et al overcomes the aforesaid problem to some extent by mounting a pair of hydraulic drive cylinders to one side of the drive path of shoring pipes and connecting the hydraulic cylinders between a foundation bracket and a slip coupling. The slip coupling functions in such a way that it grips each pipe section upon the downward, retraction stroke of the cylinder pistons, and slides freely up along the pipe section on the extension stroke of the pistons in order to grip or bite each pipe section successively so as to pull it downwardly into the ground. In the Shaw system, the maximum available driving force of the hydraulic cylinders is not utilized, because the shoring pipes are pulled down into the ground on the retraction stroke of the cylinder pistons, rather than on the extension stroke. Because of the larger piston area on the end thereof opposite its connecting rod, the hydraulic fluid pressure applied to that end of the piston will develop a greater driving force.
In U.S. Pat. No. 3,796,055, Mahony discloses apparatus for supporting and raising a building foundation wherein the hydraulic drive cylinder for the pilings is mounted to one side of the piling drive path with the cylinder mounted so that its piston does extend downwardly and is connected by a clamp to successive lengths of pilings so as to drive the piling sections into the ground upon the extension stroke of the cylinder piston and connecting rod. However, Mahony connects his drive piston to the piling sections below a foundation bracket, at a level below the footing of a building foundation, thus requiring a particularly deep and large excavation below the building foundation to accommodate his drive apparatus.
It is also noted that the patents to Shaw et al, Langenbach and Rippe all disclose the use of a tubular guide sleeve affixed or connected to a foundation-engaging bracket in such a way as to serve as a tubular guide member for the piling sections as they are driven into the ground. In the patent to Shaw et al, as well as in Langenbach U.S. Pat. No. 4,678,373, the foundation bracket assembly has a right angle shape comprising a tubular guide segment projecting vertically along the vertical face of the foundation wall, and with a generally horizontally extending member extending under the foundation footing for engagement therewith. Similar apparatus is disclosed in Gregory U.S. Pat. No. 4,695,203 as well as in May U.S. Pat. No. 4,634,319. With the systems disclosed in both of those patents, the pier-pipe or piling sections are first driven into the ground to the point of contacting bedrock or a firm resistance by a first hydraulic drive cylinder or power-driving means. Thereafter, a lifting unit or device is mounted on the top piling section above the ground and a separate hydraulic cylinder jack is then utilized between the lifting member and the building foundation structure to elevate the foundation to the desired level. Such apparatus and methods are costly and cumbersome and unduly add to the expense of foundation-shoring operations.
British Pat. Specification No. 1,418,164 is of interest for the disclosure of a foundation-supporting apparatus utilizing a pair of hydraulic cylinders to drive pilings into the ground adjacent to a building foundation. The hydraulic cylinder pistons extend upwardly and are connected to a crosshead from which connecting arms project downwardly for connection to a one-way chuck or clamp. The slip clamp slides upwardly along the piling pipes when the rams are extended, and upon the downward, retraction stroke of the rams, the chuck or clamp grips the piling and pulls it downwardly. A special frame is utilized to mount the hydraulic cylinders for proper driving operation.
A further problem encountered in utilizing foundation shoring and lifting apparatus as described above is that in apparatus such as that disclosed in Shaw et al U.S. Pat. No. 4,673,315, the foundation tends to settle downwards slightly or flex in a downward direction on each return or nondriving stroke of the hydraulic cylinder piston. Thus, as disclosed in U.S. Pat. No. 4,673,315, when the piston rods extend upwardly to take a further grip on a piling or pier-pipe section, the foundation under which the cylinder-mounting bracket is engaged tends to settle back downwardly. Such constant upward and downward movement of a foundation, even over a distance of a fraction of an inch, during pile-driving operations can be damaging to the foundation and building structure. In U.S. Pat. No. 4,012,917 to Gendron, there is disclosed a jacking apparatus for raising an offshore platform wherein a pair of hydraulic cylinders are utilized to engage and lift platform-lifting legs. Two sets of leg or pipe-engaging clamps are incorporated on the jacking apparatus in such a way that one set of clamps engages the lifting leg on the upward, extension stroke of the cylinder pistons, with the other set of clamps releasing at that time. Just the opposite occurs on the return stroke of the pistons, with the other or second set of clamps gripping the legs and preventing relative movement in the opposite direction. The Gendron double-clamp arrangement would not lend itself to utilization with building foundation supporting and lifting apparatus as described with respect to the prior art discussed above.